Joe Carr and George Flinn blast Lamar Alexander

NASHVILLE - For a low-key, even-keeled kind of a guy, Republican U.S. Sen. Lamar Alexander is nonetheless managing to ignite a lot of passion on Tennessee's campaign trail right now.

Much of it, however, is directed against the 74-year-old former governor and two-term senator by his two main GOP primary opponents, state Rep. Joe Carr, R-Lascassas, and Memphis multi-millionaire radiologist and radio station-chain owner George Flinn.

Carr and Flinn are the best known among the six challengers to Alexander in the GOP Aug. 7 primary, for which the second week of early voting starts today.

Carr and his Tennessee-based tea party supporters think they have Alexander in their sights. Carr, 56, charges the senator has "abandoned conservative principles" in areas ranging from illegal immigration to not fighting President Barack Obama, Senate Democrats and Obamacare hard enough.

Ditto for Flinn, a late entry who is largely self-funding his effort and during the second quarter put $1.8 million of his own money into the contest.

"I think that we need leadership that is energetic and is not going to sit down and give up. And that's what I'm afraid is what's happening [with Alexander]," Flinn said in an interview.

Alexander fiercely rejects that kind of talk and points to his successes in passing legislation and getting things done in some areas like student loan reforms at a time when Washington is mostly mired in gridlock.

"If we want to reverse the trend to a national school board ... we need senators who know how to do more than make speeches, who know how to get results, pass a law, make a change," Alexander said.

As for the knock that he's not sufficiently conservative, the senator called it a "pretty strange argument. I mean, how do you say that about someone who's been endorsed by National Right to Life and [has] an A rating from the National Rifle Association and been endorsed by the National Federation of Independent Business?"

Calling himself a "conservative who likes to get results," the former governor said, "I'm not in the 'shut down the government' crowd. I'm in the 'take over the government' crowd. I know that if we want to replace Obamacare or fix the debt we've got to appeal to independent voters and win a majority and actually pass laws to do that."

The next Dave Brat?

For the past month, Carr has styled himself as the next Dave Brat, the conservative Virginia economics professor who unexpectedly toppled then-U.S. House Majority Leader Eric Cantor in his Virginia congressional district's Republican primary back in June.

The underfunded Carr, who's raised only a fraction of Alexander's war chest, has picked up endorsements from celebrity conservatives Laura Ingraham, a nationally syndicated talk radio show host, and 2008 Republican vice presidential nominee Sarah Palin.

But funding from the big national "super" PACs has continued to elude Carr.

"We don't have any intention of being involved in the Senate Republican primary in the state of Tennessee," said Barney Keller, spokesman for the Club for Growth, which has backed any number of challengers to GOP incumbents.

Asked why, Keller would only say, "Sometimes we get involved in races and sometimes you don't."

The Senate Conservatives Fund did not respond to an email request for comment.

Nathan Gonzales, deputy editor of the Washington-based nonpartisan newsletter The Rothenberg Political Report, said these days one has to "pause before assuming that a sitting senator is just going to win a primary.

"But," he added, "I'll have to say it doesn't look like there's been the same consolidation of the support against the senator that we've kind of seen take place in the other races."

Gonzales' take is that Flinn's being in the race has caused the largest groups "to pause about getting in" because they may perceive a "lack of consensus on the ground."

Moreover, he said, "it is extremely difficult to beat an incumbent, particularly in a winner-take-all situation where you need to have everything to go right to thread the needle."

In Tennessee, candidates don't need a majority -- 50 percent plus one person -- to win an election. They can -- and have -- won with pluralities well below 50 percent. Outside groups' calculation may be they "not only have to beat Lamar, but we have to beat Flinn, too," Gonzales said.

One of Carr's major attacks is that Alexander didn't join with Texas Republican tea party firebrand, U.S. Sen. Ted Cruz, in his efforts to defund the federal Affordable Care Act.

Earlier this month he appeared onstage with Cruz's father before state tea party groups in Nashville where Carr lambasted Alexander for voting to end the filibuster.

"We have to take back the Republican Party from control by the establishment GOP that continues to espouse the United States Chamber of Commerce and crony capitalism and ignores the American worker and, indeed, you and I," Carr thundered.

While the elder Cruz, who often appears as a surrogate speaker for his son, didn't openly endorse Carr, just being onstage with the candidate and taking up many of the same talking points in his own speech were message enough.

Sen. Cruz's critics say the senator's efforts were ill advised, prompting a partial government shutdown over a defunding effort that wouldn't actually defund the program.

Meanwhile, Alexander has been running television ads in which he publicly took issue with Obama in a 2010 televised meeting with senators when the president took issue with claims the program would result in higher insurance premiums for millions of people.

'Amnesty,' illegal immigration flare up

Carr and Flinn hope to get traction from the resurgence of U.S. interest in immigration issues following the illegal arrival of thousands of children and teens from Central America.

Carr and Flinn both charge that Alexander's 2013 vote for an immigration overhaul amounted to "amnesty" and is responsible for the deluge. An independent watchdog, FactCheck.org, said the bill, which never passed the Senate, didn't grant "amnesty" to anyone.

Alexander has said the measure he voted for would have required beefing up the U.S. border with Mexico. The 11 million people in the U.S. illegally, Alexander has said, would in essence have to go to the back of the line for years before they could apply to become citizens. And what the nation has currently amounts to amnesty, he argued.

"I voted to end amnesty and secure the border," Alexander said.

There has been no public polling in the race since May when Vanderbilt University polled and found Alexander with solid support and Carr not being well known. A tea party group later released its own poll saying Carr was gaining and Alexander was vulnerable.

But it also showed Flinn getting some support.

Dr. John Geer, a Vanderbilt University political science professor who was involved in Vanderbilt's May poll, said while none of the national journalists calling him about the contest talk about Flinn, he could be a factor.

The GOP nominee will take on the winner of the four-man Democratic primary in which Knoxville millionaire and attorney Gordon Ball is dominating spending, largely out of his own pocket.